1. Field of the Invention
This invention generally relates to a hydraulic, adjustable vibration damper for motor vehicles. Such a vibration damper can have a damping piston fastened to a piston rod, which damping piston divides the work cylinder into two chambers that are filled with damping fluid. There can preferably be damping valves in the damping piston, and a fluid bypass can be located parallel to the valves of the damping piston. In the bypass, there can be at least one valve which reacts, or operates, as a function of the pressure. To control the bypass, there can be a device to adjust a control body of the valve, which device can be pressurized in the closing direction of the control body by means of a pressure medium. Between the pressure medium and the control body, there can be an axially movable pressure intensifier which can be sealed about the circumference thereof.
2. Background Information
One such type of vibration damper, in which a control body pressurizes a bypass with the interposition of a pressure intensifier, is disclosed by Federal Republic of Germany Patent No. 41 20 122, which has correspondence to U.S. Pat. No. 5,207,300. In this vibration damper, the pressure intensifier is pressurized by an externally applied control pressure, e.g. hydraulically or pneumatically. In such a vibration damper, a higher damping is added to a base damping, so that as a result of the high damping, the roll stability of a vehicle, or the starting conditions of a truck, can be improved, and if the control pressure drops or disappears, as a result of the internal system pressure in the decompression stage of the vibration damper, the control body can be brought into the open position and can be held there automatically. The damping force characteristic of such a vibration damper can thereby be switched so that it is either progressive or degressive. A variation of the damping force characteristic, for example, more progressive or more degressive characteristics, cannot be achieved with such a device.